Before doing a name server chage on a .IT domain you have to correcty configure the domain in the new DNS servers. If you skip this the NIC will not approve the change and the status will be "pendingUpdate".
To check whether the new dns servers are correctly configured before claiming the change, use the dns service check NIC: www.nic.it/dns-check/
Domain for which you requested a modification of the authoritative nameservers and waiting for a DNS configuration check successfully. The domain remains in this status for a maximum period of 5 (five) days. If within that period the new DNS configuration is not validated by the Registry is successful, it is abandoned. The domain back to the previous status.
To verify that the nameservers set are accepted by nic, use the whois nic: web-whois.nic.it
If the domain is in "pendingUpdate" and you have the certainty that the domain areas have been correctly configured in VS server, then it is only waiting for the NIC detect it; It might not happen right away but in the following hours.
We invite you to contact us only after verifying that the domain zone are set correctly in the new dns servers and that the state "pendingUpdate" persists even after 12 hours you needed to change the dns server from the domain control panel.